1. Field of the Invention
The present invention relates to a method for producing a liquid-discharge-head substrate.
2. Description of the Related Art
In the production of a liquid-discharge-head substrate, a silicon substrate is etched to form a liquid supply port. A silicon substrate is etched at different rates depending on plane orientations with an alkaline aqueous solution such as an aqueous solution of tetramethyl ammonium hydroxide (TMAH). A silicon substrate is subjected to anisotropic etching utilizing the difference in etching rates according to plane orientations to form a liquid supply port.
To enhance the productivity, for example, Japanese Patent Laid-Open No. 2011-51253 describes a method in which an etchant is supplied to both surfaces of a silicon substrate to simultaneously etch these surfaces of the silicon substrate.
To enhance the productivity, a silicon substrate may be etched with an etchant that has a high etching rate for silicon substrates.
According to studies performed by the inventors of the present invention, when an etchant that has a high etching rate for silicon substrates is used in the method described in Japanese Patent Laid-Open No. 2011-51253, there are cases where a liquid supply port cannot be formed so as to have an accurate opening width in the front surface on which energy generating elements are formed. Specific explanations are as follows.
First, there are cases where a protective film for protecting energy generating elements and wiring on the front surface is etched with the etchant having a high etching rate. As a result, side etching in the silicon substrate becomes less likely to be controlled with the protective film and it sometimes becomes difficult to control the opening width of a liquid supply port.
Second, although an etching sacrificial layer selectively etched with respect to a silicon substrate is used to define an opening width of a liquid supply port on the front-surface side of the silicon substrate in Japanese Patent Laid-Open No. 2011-51253, there are cases where the etching sacrificial layer is less likely to be etched with an etchant having a high etching rate. Thus, there are cases where it is difficult to control the opening width through the use of the etching sacrificial layer.